In 1956 began the Silver age of Comic Books with the return of the preference for superheroes, such as Flash and Green Lantern by DC Comics. If Dell Comics and its comics for children remained the leading publisher of comic books, genres other than superheroes started to decline and many publishers closed. Very popular superheroes, mainly created by Stan Lee and Jack Kirby, appeared in Marvel Comics. This turned into the leading publisher of comics in the next period known as the Bronze Age of Comic Books (from the early 1970s to 1985) during which the stories became less manichean while superhero comics maintained their hegemony. The distinction between these two periods is often associated by historians to an event but it is rather a series of changes that affected many aspects of the comics world. At the same time, underground comics appeared, which, aesthetically, addressed new themes, and economically, were based on a new distribution model. Comic strips continue to be distributed throughout the country and even some of them gained international dissemination.